Browsing by Author "Musierowicz, Kazimierz"

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    Elimination of the intermittent earth faults
    (Видавництво Національного університету «Львівська політехніка», 2003) Lorenc, Jozef; Marcinkowski, Zygmunt; Musierowicz, Kazimierz
    In the paper, the subject of the intermittent earth faults and their detection has been discussed. The intermittent faults belong to a group of hardly detectable ones due to the low and unstable measuring signals. The analysis has been carried out for typical medium voltage distribution network under faults with different characteristics. It was shown that the criterion magnitudes used up to now in the to-ground protections can be ineffective here. Influence of various methods of the measuring signals filtration (Morlet wavelet filter, averaging filter) on the criterion values of protections has been assessed. An original algorithm with logic inertia improving the effectiveness of the to- ground protection under intermittent fault conditions has been proposed.
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    Fault discrimination by power protections during transient disturbances
    (Видавництво Національного університету «Львівська політехніка», 2003) Musierowicz, Kazimierz; Marcinkowski, Zygmunt
    During first dozens of milliseconds from the moment when the fault occurs, the transient components due to the fault can appear in the short circuit currents and voltages. The latter could have a form of either the attenuated oscillating components or the non-periodical components making troubles to be filtered. Then, the highly inconvenient conditions for the fast short-circuit protections can appear due to specifics of the measuring signals disturbances the separation of which is very difficult. Traditionally, the measuring signals disturbances are eliminated using either the Fourier transform (FT) or the Fast Fourier Transform (FFT). The different tool of signal analysis is the wavelet transform (WT). In the paper, referring to an example of typical non-stationary signals, a comparison of the both analysis methods referred to the protective measuring algorithms is carried out. A special attractiveness of the wavelet transform is proven.